Dry hydrogen chloride



June 8, 1943. R. L. coMsTocK DRY HYDROGEN CHLORIDE Filed Dec 10, 1840 L. Camsfoak Patented June 8, 1943 PATENT OFFICE nayjarinrocu-zu CHLORIDE Rock nboms'thcaweeks, La., assignor to Bay Chemical Company, Inc, New Orleans, La., a corporation'of mama -nasal." 10, 1940, Serial No. 369,488

umns and conde mentsjofheatand novel ieature'so a pointed outin'the appende claim 4 Claims. (Cl. 23-154) This invention relates to producing dry HCl from aqueous hydrochloric acid of any concentration, and particularly from dilute hydrochloric acid solution.

Various proposals have been made for concentrating hydrochloric acid, but have been objectionable in point of need forexpensive equipment, or of costs of operation. Special materials of construction have been required inasmuch as ing heat transfer surfaces.

HCl thereby without requirin The present inveptionay as ractionatingcolsupply-" apparatus that is 40 higher require! 1 v terial or steel lines with tile, for example.

In the drawing, Figure 1 is a diagrammatic representation of a flow sheet including means to produce dry HCl from dilute hydrochloric acid according to this invention.

Broadly, according to the principles of this in- V vention, muriatic acid is concentrated by heating the acid in the presence of solid anhydrous CaClz with gradual elevation of temperature approximately to that of boiling 50% aqueous CaClz the acid is corrosive. For commercially feasible solution. This temperature is approximately 125 operations, expensive fractionating columns have C. Preferably the dilute acid flows over a column been required and considerable volume of liquid of the CaClz in the form of solid lumps with has had to be circulated. gradual rise of temperature to about 125 C. The An important purpose is to obtain directly from HCl evolved flows countercurrently to the liquid dilute aqueous hydrochloric acid a dry gas of over and into contact with progressively drier CaClz. 99% E01, or even containing less than 0.3% Heat of solution is released from the solid CaCli water. A particular object is to obtain dry HCl 4 and additional heat is supplied to the eflluent from dilute aqueous acidinone step. CaClz solution. Thus, concentration of HCl is An object also is to utilize dehydrating maefiected by removal of water gradually through terial of such nature and in such manner as to fractional distillation of dilute muriatic acid in facilitate regenerating the material inexpensively the presence of solid CaClz, both distilland and and with but low loss of material, as-contrasted distillate contacting solid CaClz with the residual with sulphuric acid on re-concentration. distilland gradually forming a solution of in- A further purpose of thi invention i to obtain creasing concentration of CaClz and gradually bedry HCl from dilute acid by removal of water mg heated to about 125 C. Inpreferred practice from the entire system simply and substantially the eflluent CaClz solution flows countercurrently automatically. toa supply of steam or supply of hot gas of ex- An important purpose also is to introduce ceedingly little or of no content of HCl. Such is requisite heat into the dehydrating system simply I provided conveniently-by boiling eflluent CaClz and directly by an improved method of minimizsolution and leading the heated vapors therefrom into thecolumn. I Also an object is to economiz ein fuel or heat energy to produce dry HCl" from aqueous commercial grade muriatic acid of any concentration. An important object of g'this invention more-. over, is to concentrateidilute .muriatic acid in equipment of cheap construction e'and 'togobtai'n, tionatirigc'ol- Reference may bemade'more particularly to the iac'companying drawingfand description of irritable-apparatus tocarry on this invention. It willbe-understood however that the invention is not necessarily limited to these-particular illusm. and E diments, but m y bev executed .otherwis'e. I r

I In thedrawingis shown a tower I. This may be constructed of inexpensive material resistant to muriatic acid, such asbrick, or resinous ma- '1 'someintermediate'point is aninlet 2 to introadaptable toobtain dry Hciiga 'eith r p' e'ri odi 3 cally or. continuously from. dilute aqueous acid.

Also, object is to dehydrate hydrochloric ciples of this invention.

sh n n he p anying drawing, while entionar part cularly du'ce' diluteacid-liquid. The tower is filled with anhydrous solidfCaCh in the form of lumps or 1 I I chunks 3 which may be supplied to the tower acid with substantial avoidance ot-circulating Ifhese objects and otherswillbe'iapparent from the following illustrative description. of the prinbyuneanssuch as the valved hopper 12 located at the'lupper end of the-tower. These ofier concsiderablefsurface area .both to the down-flow of 5,0

aqueous jacid and'to the up-flow of HCl gas removed from the aqueous acid. The lower end of the tower opens into a suitable receiver 4 for eflluent CaClz solution.

The receiver 4 is connected with a suitable boiler 4a so that heated vapors may be conducted I of the CaCh solution and even to produce anhydrous CaCl: therefrom, such as spray tower I and rotary drum 8. A flue 9 is provided to convey hot gases from drum 8 into spray tower I. A suitable source of heat is combustion chamber l discharging into rotary drum 8. In drum 8 are contained lumps of solid CaClz.

In the flow of material through this system, aqueous HCl of any desired concentration may be introduced to the lumps of anhydrous CaClz in dehydration column 3. Preferably, the acid inlet'2 is at about the middle of dehydration tower I. From the incoming aqueous acid the anhydrous CaCl: at once abstracts a considerable amount of water, with corresponding evolution of heat. Thus the solution of CaClz is formed and flows with the progressing acid solution through the lumps of CaClz. Progressively, water is abstracted from the acid to form CaCl: solution while HCl and water vapor flow against the solution to the drier endof the CaClz'coIumn. As the flowing solution increases in concentration of CaClz the solution gradually becomes depleted in HCl. As this solution progresses, heat is introduced into the eiiiuent liquid so that the liquid becomes increasingly impoverished in HCl. The heat input may be regulated so that the eflluent CaCl-z solution is at a temperature of about 125 C. Thus-the eflluent liquid is automatically regulated to contain about 50% CaClz. To eflect this heating and sweeping out of HCl, CaCh solution in receiver l at the end of the CaClz column is heated to boiling. Preferably, a portion of the liquid in receiver 4 is withdrawn to a separate boiler la from which steam, which may contain minor amounts of HCl, is conducted into the bottom of CaClz column 3.

Thus any residual HCl is introduced immediately into the descending column of CaClz solution.

From receiver 4 the CaClz solution is withdrawn suitably for removal of water and for recovery of CaClz. The CaCl: may be returned to the system in the form of lumpsifor introduction into the top of the dehydrating tower or may be re-introduced at higher temperature into the CaCh reservoir 4 at the bottom of the dehydrating tower.

The CaCl: solution, when suitably increased in concentration, is an appropriate medium for introduction of heat to the system. However, this means of introducing heat into the system constitutes an alternative that may not necessarily be suitable in all cases, particularly where.

pumping costs would be burdensome. Nevertheless, concentration of the CaClz solution may be effected conveniently. in an atmosphere of hot gas in spray tower I. Water vapor is eliminated from the system at the upper portion of the tower I. The liquid flow through tower I may be regulated by simple control so as to yield a solution of approximately 70% of CaCla at the bottom of the tower I. This relatively concentrated solution is at considerably higher temperaturethan the more dilute solution of 50% (Jack at the bottom of the dehydrating column. This heat energy may be introduced directly into the solution in receiver-l even to maintain boiling thereof and without requiring heat interchangers.

A portion of CaCl: solution may be dehydrated in heated rotary drum 8. Lumps II of CaCh in drum 8 promote evaporation of incoming solution while rotation of the drum and consequent agitation promotes formation of lumps rather than of dust. The lumps are removed in conventional manner from drum 8.

Evaporation in drum-l is brought about by hot gases introduced to above 400 C. from furnace Ill. These hot gases, mingled with steam from the evaporating solution of CaClz, flow into tower lat relatively high temperatures so as to evaporate water readily in spray tower l and to I concentrate the dilute CaCh being sprayed therein. The cooled combustion gases leave the system mingled with water vapor. The calcium chloride lumps in the tower i may be replenished from time to time from the hopper l2 s0 as to maintain the column above the point of introduction of the hydrochloric acid, making the process continuous.

In operation of dehydrating tower l,- the column of solid anhydrous CaClz moves downwardly readily in contact with incoming dilute aqueous acid and in contact with steam rising in the lower end of the column. In the tower essentially fractional distillation occurs within the column of Catch, with a solution of water, CaCl: and HCl of constantly changing concentrations being in contact with solid CaClz. Water already in the system in theform of CaClz solution at the bottom of the tower serves, when vaporized from accumulated CaClz solution, to heat and to distill the eflluent CaCh solution.

This occurs without increasing the accumulation of water in the system and is counteracted by appropriate withdrawal of the accumulated CaClz solution for concentration.

Conditions in the dehydrating tower are maintained substantially constant automatically by the descending CaClz column in the upper part of the column. The evolved HCl vapors rise into progressively drier portions of CaClz with accompanying evolution of heat of solution of CaCl-z. This progressive heating and distillation to drier parts of the column accomplishes substantially complete removal of water vapor so that the eflluent gases from the top of the column contain over 99% HCl and contain even as little as 0.3 or 0.2% water. At the lower end of the column eflluent solution may be maintained by control of the rate of boiling and by the rate of removal of solution for dehydration at approximately 125 C. This corresponds to approximateLv CaClz solution. Under these conditions the efllciency is such that CaClz in receiver 4 may contain only, about 0.25% HCl.

heating means of conventional nature, if desired.

While in accordance with the patent statutes I have set forth the principles of this invention and have illustrated a preferred practice thereof by specific example, it will now be apparent to those skilled in the art that modifications may be made within the scope of the appended claims.

What I claim is:

1. A process for producing substantially anhydrous hydrogen chloride comprising contacting a moving column of solid lumps of calcium chloride with liquid aqueous hydrogen chloride solution wherein said solution is introduced into the column intermediate the ends thereof, pro gressively dissolving the solid calcium chloride in the said hydrogen chloride solution and progressively evolving hydrogen chloride as the materials move toward one end of the column, simultaneously progressively increasing the temperature of the materials as they move toward said end, removing the calcium chloride from said end as a spent heated aqueous solution, progressively dehydrating hydrogen chloride gas evolved from the aqueous solution by-contacting the evolved hydrogen chloride gas with the solid calcium chloride intermediate the point of introduction of the aqueous hydrogen chloride solution and the opposite end of the column, and withdrawing substantially anhydrous hydrogen chloride gas from said opposite end of said column.

'2. A process for producing substantially anhydrous hydrogen chloride comprising contacting a moving column of solid granular calcium chloride with liquid aqueous hydrogen chloride solution wherein said solution is introduced into the column intermediate upper and lower ends thereof, progressively dissolving the solid calcium chloride in' the said hydrogen chloride solution and progressively evolving hydrogen chloride as the materials move toward the lower end oi. the column, simultaneously progressively increasing the temperature of the materials as they move toward said lower end, removing the calcium chloride from said lower end as a spent heated aqueous solution, progressively dehydrating hydrogen chloride gas evolved from the aqueous solution as a result of the heating operation by contacting the evolved hydrogen chloride gas with the solid calcium chloride intermediate the point of introduction of the aqueous hydrogen chloride solution and the upper end or the column, and withdrawing substantially anhydrous hydrogen chloride gas \from said upper end or said column.

3. A process forproducing substantially anhydrous'hydrogen chloride comprising contacting a moving column of solid granular calcium chloride with liquid aqueous hydrogen chloride solution wherein said solution is introduced into the column intermediate the ends thereof, prothe opposite end of the column, withdrawing 4 substantially anhydrous hydrogen chloride gas irom said opposite end of said column, and re covering the calcium chloride.

4. A continuous process for producing substantially anhydrous hydrogen chloride comprising contacting a moving column of solid lumps .of calcium chloride with liquid aqueous hydrogen chloride solution wherein said solution is introduced into the column intermediate the ends thereof, maintaining the column of lumps oi calcium chloride anterior to the point of introduction oi the hydrogen chloride solution, progressively dissolving the solid calcium chloride in the said hydrogen chloride solution and progressively evolving hydrogen chloride as the materials move toward the posterior end of the column, simultaneously progressively increasing the temperature of the materials as they move toward said posterior end, removing the calcium chloride from said posterior end as a spent heated aqueous solution, progressively dehydrating hydrogen chlortde gas evolved i'rom the aqueous solution by contacting the evolved hydrogen chloride gas with the solid calcium chloride intermediate the point of introduction of the aqueous hydrogen chloride solution and the anterior end or the column, and withdrawing substantially anhydrous hydrogen chloride gas from said anterior end of said column. 7

ROCK L. COMSTOCK. 

